This invention relates generally to photometer spheres including a spherical interior encompassed by a diffusely reflecting wall, provided with apertures for incident light as well as for applying samples and photo detectors in the diffusely reflecting wall.
The optical integration properties of such diffusely reflecting photometer spheres known as "Ulbricht spheres" are utilized for many measurements in light engineering, (ULBRICHT, R., Die Bestimmung der mittleren, raumlichen Lichtintensitat durch nur eine Messung (The Determination of the Medium, Spatial Light Intensity by Only One Measurement); ETZ (Electrotechnical Magazine) 21 (1900), pages 595-597.
Numerous more or less modified Ulbricht spheres find application in various photometer apparatus (cf. e.g. HELBIG, E.: Grundlagen der Lichtmesstechnik, AVG Publishing House Leipzig (1972); DIN 5033; German Offenlegungsschrift No. 2,606,675 and German Offenlegungsschrift No. 2,757,196; KORTUM, G.: Kolorimetrie, Photometrie und Spektrometrie, Berlin, Springer Publishing House (1955); prospectus of Nixdorf Computer AG, 4790 Paderborn: Nixdorf Computer in der Farbmetrik).
All known photometer spheres have the following disadvantages:
(1) Contamination of the diffusely reflecting coat of the internal wall and thus time-dependent variation of the integration properties. Measurement inaccuracies and the necessity of renewing the costly coat from time to time thereby resulting. PA0 (2) The sample is not permitted to be of a liquid or partially liquid consistency, which occurs, however, quite often, e.g. for color measurements (humid samples such as paper, textiles, organs containing blood such as liver, brain etc.). PA0 (3) Complicated production (interior must be geometrically spherical as precisely as possible). PA0 (4) High production cost and permanent operation cost for renewing the remission coat.